Field of the Invention
This invention relates generally to a process for stiffening and/or strengthening thin panels and, more particularly, to a process for stiffening and/or strengthening trim panels for a vehicle that includes securing micro-truss reinforcement patches on an opposite surface of the trim panel from the show surface.
Discussion of the Related Art
Trim panels on a vehicle, such as fascias, rockers, door moldings, etc., often have an outward facing show surface, sometimes referred to as a class-A surface, that gives the panel an aesthetically pleasing appearance. Providing such show surfaces typically requires relatively expensive materials and manufacturing processes. Thus, trim panels are typically made very thin to conserve cost. However, such trim panels often times have a two-dimensional or three-dimensional curvature and are required to be stiff enough to resist various loads without excessive deformation. In response to this, it is known in the art to make a trim panel as a two-piece structure including an outer show surface panel and an internal support structure often including a series of stiffening ribs forming a frame that provides structural integrity. The support structure may include a series of welding pads integrated into the support structure at locations where the ribs cross. The welding pads have the general shape of the show surface panel and are used to ultrasonically weld the support structure to an inside surface of the show surface panel. The stiffness of the trim panel is set mainly by the height, thickness and spacing of the ribs.
In order to reduce cost and weight, it is desirable to limit the number of ribs in the support structure, which also reduces its stiffening capability. Thus, the ribs are generally selectively positioned and provided with different heights depending on where the structural integrity of the particular trim panel is desired. However, the height of the ribs is limited by the packaging volume of the trim panel. Further, although the show surface panel does possess some inherentstiffness, most of the stiffness is provided by the rib structure. Therefore, in order to further reduce the cost of the trim panel, it is desirable to make the show surface panel as thin as possible consistent with the ability of the support structure to provide the desired rigidity. However, because the support structure is welded to the show surface panel, there are limits as to how thin the show surface panel can be because the welding operation could cause imperfections on the show surface of the show surface panel if it is too thin.
It is known in the art to fabricate a three-dimensional micro-truss polymer structure for various structural uses. For example, U.S. Pat. Nos. 7,653,279 and 7,382,959 disclose a process for fabricating such a micro-truss structure. Generally, the process includes providing a reservoir or mold filled with a volume of a curable monomer and covered by a mask including strategically positioned apertures. Light sources are positioned relative to the mask and light from the light sources shinning through the apertures cures and hardens interconnected polymer columns, referred to herein as struts, to form a rigid support structure. Once the columns are cured, the struts are formed and the light sources are turned off, the reservoir is emptied of the non-cured monomer that did not receive the light so that the resulting hard polymer structure forms the micro-truss structure having an array of spaced apart struts.